Where to start coding up a drawing app?

I'm trying to figure out where to start with coding up a drawing app because I can't find one that does what I want. I can kind of brute force it in Autodesk's SketchBook. I'd like a thing that does what I want more conveniently and better. It appears to not exist. I've spent some time looking.

I've found one video for creating a drawing app in JavaScript.

I've repeatedly had Python recommended to me over the years as the first programming language I should learn. I'm happy to pursue JavaScript instead or another language if that would serve this goal better.

I've discovered MIT App Inventor and they do have drawing app tutorials. I completed the first Doodle app tutorial and synced it to my phone and tried the working demo on my phone.

If my app idea does what I want and does it well, I think I could sell it. In theory, MIT app inventor allows for that. In practice, it seems unlikely to me that this is really viable.

If you know how to take something from MIT app inventor and sell it via Google Play, I'm all ears. But I'm also doubtful I can even get the functionality I want via this Lego-for-apps system and I already know some HTML and CSS and I do a little website work for pay in the small town I live in. So I'm thinking it would make more sense to code it myself, both to get the functionality I desire and to own the code so I can potentially monetize it.

I'm looking for any ideas where to start. I'm fine with hearing "It's time for you to just start that free course that guy recommended to you back in March." (See below) But I'm a little leery of starting it only to discover it is yet another dead end and I've wasted a bunch of time that could have been better spent coding the app in a different language.

Back in March, someone from HN talked with me via Discord about learning to code and recommended a free Python course. Notes and link to course are here.

In March, I also learned my computer didn't have enough RAM. That has since been remedied.

In the process of applying for a thing around the same time, I also theoretically acquired free access to some initial coursework via a boot camp, assuming I can remember my login credentials.

HN Discussion

Originally posted to HN as an Ask HN. It got no traction, which is annoying the fool out of me this evening cuz REASONS.